Liquid control system for washing machine

ABSTRACT

A liquid control system for a washing machine having a bidirectional motor operable for effecting washing and extraction operations includes a one-way check valve in the drain conduit. The liquid control system includes a pump driven by the motor and operable for pumping toward and from a tub during the washing and extractions, respectively, with the check valve being self actuating for permitting flow from the tube during the extraction operation and preventing backflow to the tub at the conclusion of the extraction operation and during the washing operation to effectively obviate mixing of the washing liquid with residual liquid from the previous cycle.

United States Patent Smith LIQUID CONTROL SYSTEM FOR WASHING MACHINE[72] Inventor: Thomas R. Smith, Newton, Iowa [73] Assignee: The MaytagCompany, Newton,

Iowa

[22] Filed: July 6,1971

[2]] Appl.No.: 159,825

[52] U.S.Cl.... ..68/23.4

[51] Int. Cl. ..D06f 39/08 [58] Field of Search ..68/23.4, 208

[56] References Cited UNITED STATES PATENTS 2,923,144 2/1960 Smith..68/208 X 2,924,959 2/1960 Israel ..68/208 X 2,972,877 2/1961 Platt..68/208 X 3,027,908 4/1962 Cochran ..68/208 X 3,078,861 2/l963Miller.., ..68/208 X [451 Sept. 19, 1972 FOREIGN PATENTS OR APPLICATIONS636,598 5/l962 Italy ..68/208 Primary ExaminerWilliam I. PriceAttorney-William G. Landwier et a].

[5 7 ABSTRACT A liquid control system for a washing machine having abidirectional motor operable for effecting washing and extractionoperations includes a one-way check valve in the drain conduit. Theliquid control system includes a pump driven by the motor and operablefor pumping toward and from a tub during the washing and extractions,respectively, with the check valve being self actuating for permittingflow from the tube during the extraction operation and preventingbackflow to the tub at the conclusion of the extraction operation andduring the washing operation to effectively obviate mixing of thewashing liquid with residual liquid from the previous cycle.

8 Claims, 5 Drawing Figures LIQUID CONTROL SYSTEM FOR WASHING MACHINESUMMARY OF THE INVENTION This invention relates to a liquid controlsystem for a washing machine and more particularly to a system includinga check valve and operable for preventing intermixing of residualliquids remaining in the drain conduit with the fresh washing liquid.

In the art of washing machines, the prevention of intermixing of thewashing liquid with residual liquid from the previous washing cycle isreceiving increasing attention. In some constructions, the washingcontainer is effectively isolated from the liquid basin so that theproblem of liquid intermixing is obviated, but in other constructions, aperforate washing basket is disposed within a generally imperforateouter liquid tub having a conduit communicating with the drain. In'these constructions, washing liquid that is pumped from the outer tubtoward the drain is substantially removed from the washing machine but aresidual quantity remains in the drain conduit and may be of sufficientquantity to return to the outer tub upon interruption of the pumpingoperation and upon the liquid seeking a static level. I

The potential objection to residual washing liquid intermixing withwashing liquid for succeeding cycles is even greater in washing machinesin which a bidirectional drive system operates in one direction toeffect washing operation and in the opposite direction to effect acentrifugal extraction and pumping operation. With this type of drivesystem the pump is effectively operable for pumping liquid toward thetub from the drain hose during the washing operation.

It is therefore an object of the instant invention to provide animproved washing machine liquid control system operable for preventingintermixing of residual liquid from a previous operation with freshwashing or rinsing liquid.

It is a further object of the instant invention to provide an improvedwashing machine control system having a one-way check valve disposedbetween the liquid container and the pump. operable in It is a furtherobject of the instant invention to provide, in a washing machine havinga bidirectional drive system operable for pumping liquid from the tubduring an extraction operation and toward the tub during a washingoperation, a liquid control system including a check valve disposedbetween the pump and the outer tub to prevent intermixing of residualliquid from a previous operation with the fresh liquid in the tub.

It is yet a further object of the instant invention to provide animproved liquid control system for a washing machine and including acheck valve disposed between the tub assembly and the pump forpermitting pumping of liquid from the tub assembly and operable forpreventing backflow of liquid into the tub in the absence of pumping andfor preventing liquid flow into the tub assembly from the drain systemunder high pressure reverse pumping conditions.

These objects are achieved in a liquid control system for a washingmachine wherein a one-way check valve is disposed between theliquid-containing tub assembly and the pump and is self actuable to asealed condition with a low urging force for preventing low pressureliquid flow into said tub assembly and further responsive to a higherurging force for preventing high pressure liquid backflow into said tubassembly to avoid intermixing ofliquid in the washing container.

Operation of the device and further objects and advantages thereof willbecome evident as the description proceeds and from an examination ofthe accompanying two pages of drawings.

DESCRIPTION OF THE DRAWINGS The drawings illustrate a preferredembodiment of the invention with similar numerals referring to similarparts throughout the several views wherein:

FIG. 1 is an overall view of an automatic washing machine with variousportions broken away to show components of the improved liquid controlsystem of the instant invention;

FIG. 2 is a longitudinal sectional view of the check valve constructionused in the liquid control system of the instant invention as takenalong lines 2-2 of FIG.

FIG. 3 is a transverse sectional view of the inlet portion of the checkvalve as taken along lines 33 of FIG. 2;

FIG. 4 is an enlarged fragmentary sectional view of the low pressuresealing condition of the check valve; and

FIG. 5 is a fragmentary sectional view similar to FIG. 4 showing a highpressure sealing condition of the check valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, thereis shown an automatic washing machine including a base frame 10supported on a plurality of adjustable legs 11 and mounting a cabinet 13comprising sidewall portions 14 and a top cover portion 15. The topcover portion 15 includes a hinged door panel 16 normally covering arecessed loading opening 19 and further includes an upwardly extendinghousing 20 for accommodating various control members such as programmingmeans actuable by the dial 21.

Mounted within the cabinet 13 is a tub assembly 23 nutationallysupported on the base frame 10 by an inverted tripod arrangementincluding tub braces 25 which are connected at the lower end to asupport member 26 positioned on the base frame 10. The tub braces 25 areconnected at their upper ends to a generally imperforate outer liquidcontainer or tub 29. The tub braces 25 are also resiliently connected tothe base frame 10 by means of centering springs 30 which resist rotationof the support member 26 relative to the base frame 11 but permitnutational movement relative to the base frame 1 1.

Revolubly mounted in the imperforate outer tub 29 is a perforate clothesbasket or inner tub 31 in which is positioned an oscillatable agitator33 for effecting movement of fabrics and washing liquid within the tubassembly 23. The imperforate outer tub 29 and the perforate inner tub 31are substantially aligned with theloading opening 19 in the top cover 15for permitting the operator to place fabrics within the inner tub 31 andto remove them upon completion of the cycle. thru inclusive shown Thebase frame also supports, through a motor mount 34, a reversible drivemotor 35 operable in a bidirectional drive system for selectivelyeffecting oscillation of the agitator 33 or centrifugal rotation of theinner tub 31. The drive system for selectively effecting operation ofthe agitator 33 and rotation of the inner tub 31 includes a doublegroove pulley 36 fixed to the shaft of motor 35 and drivingly engagedwith a main drive belt 39 which in turn is drivingly engaged with themain drive pulley 40. The main drive pulley 40 is drivingly 99 with themain drive pulley 40. The main drive pulley 40 is drivingly connected toeither the agitator 33 through a drive shaft (not show) and the gearingof a transmission 41 or to the inner tub 31 through the housing of thetransmission 41 and a clutch (not shown).

Operation of the motor 35 in a first direction effects rotation of themain drive pulley 40 for effecting oscillation of the agitator 33through the drive shaft (not shown) and transmission gearing. Operationof the motor 35 in the opposite direction effects rotation of the drivepulley 40 and the transmission 41 through the clutch (not shown) forrotating the inner tub 31 to effect centrifugal extraction of liquidfrom fabrics within the inner tub 31. g

The washing machine is provided with controls for programming themachine through a sequence of operations including energization of themotor 35 for operation in a first direction to effect a washing and/orrinsing function followed by energization of the motor 35 in a seconddirection to effect a liquid extraction function.

The construction and mounting of the tub assembly 23 and the operationof the inner tub 31 and agitator 33 for effecting washing and extractionoperations are more clearly and specifically shown in the followingpatents, each of which is assigned to the assignee of the instantinvention: Scott et al. US. Pat. No. 2,854,297; Smith et al. US. Pat.No. 2,926,136; Burkland U.S. Reissue Pat. No. RE 25,157; and GoodlaxsonUS. Pat. No. 3,013,645.

The base frame 10 also supports a pumping means 42 that is driven by thebidirectional motor 35 through the motor-mounted pulley 36, the pumpdrive belt 43 and the pump-mounted pulley 44. The pump 42 communicateswith the outer tub 29 through a conduit 45 and is operable for carryingliquids the the outer tub 29 and pumping them toward an external drainthrough a drain hose 49 and standpipe 50 when the motor 35 is operatedin the direction for effecting centrifugal rotation of the inner tub 31.Since the pump 42 is drivingly connected to the bidirectional motor 35and is operable in the first and second directions with the motor 35,the pump 42 will tend to pump liquids toward the outer tub 29 throughthe conduit 45 when the motor 35 is operating in the direction foreffecting agitation of the fabrics during the washing portion of cycle.

In installations of the washing apparatus wherein a relatively longelevated drain hose is provided or wherein a standpipe drain is utilizedas in FIG. 1 the drain hose 49 is capable of retaining a significantquantity of liquid at the termination of the pump-out or extractionperiod. This retained liquid, in the absence of a check valve in theline between the pump 42 and the outer tub 29, tends to return towardthe outer tub 29 as the liquid seeks a stabilized level. This backflowof liquid toward the outer tub is considered by some as undesirablesince there may be intermixing of the residual used washing liquid withthe fresh washing liquid of the succeeding cycle and it is thereforepreferred that the backflow into the outer tub be prevented.

As will be shown in greater detail hereinbelow, a check valve assembly51 in the liquid system of the instant invention is operable forpermitting relatively free liquid flow from the outer tub 29 to the pump42 and thus to the drain during pump out while preventing backflow ofused washing liquid into the outer tub 29 upon termination of the pumpout and during the succeeding washing operation.

Referring to FIG. 2, there is shown a longitudinal sectional view of thecheck valve assembly 51 as used in the liquid control system forpreventing the backflow of washing liquid into the washing container ofa fabric washing apparatus for example. The check valve assembly 51 isconnected between the outlet 53 of the outer tub 29 and the fluidconduit 45 leading to the pump 42. The check valve assembly 51 includesa housing 55 formed of a relatively rigid plastic to which the fluidconduit 45 is connected at the lower end by a clamp 56. The check valveassembly 51 further includes an upper tubular member 59 formed of aresilient elastomer material and retained on the tub outlet 53 by aclamp 60. An enlarged portion 61 of the housing 55 internally receives aflange portion 63 of the tubular member 59 and the mating parts aresecurely held together by a retaining ring 64. The enlarged portion 61of the housing includes a plurality of radially inwardly extending ribs65, as best shownin FIG. 3, which are aligned with grooves 66 in theretaining ring 64 for initial assembly. The retaining ring 64 is thenrotated, such as with a tool engageable with holes 67, cut into the ribs65 to securely connect the housing 55 to the tubular member 59. A washer69 is disposed between the retaining ring 64 and the flange portion 63of the tubular member 59.

The check valve assembly 51 further includes a thin pliable resilientseat member 70 disposed between the flange portion 63 of the tubularmember 59 and the housing 55. The seat member 70'includes an outerannular ring 71 mating with a groove 73 in the housing 55 and isretained in position by the clamping action between the flange portion63 and the offset in the housing 55. The seat member 70 includes a thinannular lip 74 extending into the housing passageway and defining asufficiently large central opening to permit relatively free flow ofliquid in a downward direction through the check valve assembly 51.

A lower surface 75 of the radially outwardly extending flange portion 63of the tubular member 59 defines a secondary seat or backup seat forengagement by the inwardly extending thin pliable lip 74 of the primaryseat member 70 to insure a high pressure seal against backflow of fluidin the upward direction.

The check valve assembly 51 includes a spherical valve member looselyretained in the housing 55 and, in the absence of an upward pressure,supported on a plurality of ribs 81 formed internally to the housing 55.The movable valve member 80 may be formed of a styrene copolymer orsimilar lightweight material and includes a generally solid lowerportion 83 and a hollow upper portion 84 molded as separate halves. Thetwo halves may be solvent welded to form a buoyant, unbalanced,ball-like valve member 80 movable within the housing 55 in apredetermined orientation so that a surface free of flash lines isalways oriented for engagement with the lip 74 of the resilient seatmember 70.

As previously indicated, the ball valve member 80 is buoyant and upon arise of liquid in the conduit 45 leading from the pump 42 to the tuboutlet 53, such as occurring at termination of a pump-out operation,will rise to engage the lip 74 of the primary valve seat 70 as showninFIG. 4. This seal is effected by relatively low pressures such as arepresent with a rising liquid level acting on the valve member 80. Theseal is sufficient to prevent passage of liquid beyond the seal member70 so that used washing liquid is not returned into the outer tub 29upon cessation of the pumping action at termination of the extractionoperation.

In a construction as shown in FIG. 1 wherein operation of the pump 42 inan opposite direction tends to pump liquid toward the outer tub 29, itis important that a high pressure seal be effected to prevent therecirculation of liquid into the tub 29 under the force of the pump 42.Such a high pressure seal is effected in FIG. 5 wherein the higherpressure of the liquid in the backflow direction forces the movablevalve ball member 80 further upwardly in the check valve so that theprimary valve seat 70 flexes into engagement with the secondary valveseat comprising the lower surface 75 of the flange portion 63 so as toback up the primary seat for effecting a relatively high pressure fluidseal.

In a specific construction for the check valve, the primary valve seat70 is formed of an ethylene propylene terpolymer having a durometer ofapproximately 40 Shore A and includes a lip portion approximately 0.020inch in thickness and defining an opening approximately 7/8 inchdiameter. The secondary valve seat defined by surface 75 is formed ofsimilar material having a durometer of approximately 80 Shore A and aflange thickness of approximately five-sixteenths inch. In this specificexample, the movable valve member is molded of a styrene acrylonitrilecopolymer in approximately a one inch spherical ball. The movable valvemember is operable to sealingly engage the primary seat at low pressuresresulting from only the buoyancy force of water acting on the movablevalve member when approximately half submerged in the rising liquid.I-Iigh pressures for this specific embodiment are in the general area of5 psi and result from the reverse operation of the pump as is presentduring the washing portion of the cycle of operations.

This liquid control system is shown in a copending application entitledVALVE CONSTRUCTION filed on even date with this application by GordonJerry Davis and assigned to the assignee of the instant invention.

It is therefore seen that the liquid system disclosed herein including aone-way check valve in the conduit between the outer liquid containingtub and the pump permits advantageous operation by preventing the returnof used washing liquid into the washing system following completion ofthe extraction operation and the termination of the pumping. Thisself-actuating system is reliable and permits the advantageous use of abidirectional drive in a washing machine for achieving washing andextraction operations without employing auxiliary pumping systems orcontrol systems.

In the drawings and specification, there has been set forth a preferredembodiment of the invention and, although specific terms are employed,these are used in a generic and descriptive sense only and not forpurposes of limitation. Changes in form and the proportion of parts aswell as the substitution of the equivalents are contemplated ascircumstances may suggest or render expedient without departing from thespirit or scope of this invention as defined in the following claims.

Iclaim:

1. In an apparatus for performing a washing operation and a liquidextraction operation, the combination comprising: means for effectingsaid washing and liquid extraction operations including an outer tub forcontaining washing liquid and having a drain outlet in a lower portionthereof, a perforate inner tub for containing articles to be washed insaid liquid, and agitation means within said inner tub; means includinga motor for operating said agitation means during said washing operationand for rotating said inner tub during said extraction operation;conduit means effectively connecting said drain outlet to an externaldrain; pump means associated with said conduit means and driven by saidmotor for effecting flow of washing liquid from said outer tub towardsaid extemal drain when said motor is operated as during said extractionoperation; and one-way check valve means in said conduit means andoperable for permitting generally free flow of liquid from said outertub toward said external drain as during said extraction operation andresponsive to residual liquid in said conduit means for preventingbackflow of said residual liquid into said outer tub.

2. In an apparatus for performing a washing operation and a liquidextraction operation, the combination comprising: means for effectingsaid washing and liquid extraction operations including an outer tub forcontaining washing liquid and having a drain outlet in a lower portionthereof, a perforate inner tub for containing articles to be washed insaid liquid, and agitation means within said inner tub; means includinga reversible motor operable in a first direction for operating saidagitation means during said washing operation and operable in a seconddirection for rotating said inner tub during said extraction operation;conduit means effectively connecting said drain outlet to an externaldrain; pump means associated with said conduit means and driven by saidreversible motor for effecting a pressure head in the direction of saidouter tub with said motor operating in said first direction as duringsaid washing operation and for effecting a pressure head in thedirection of said external drain when said motor is operated in saidsecond direction as during said extraction operation; and one-way checkvalve means in said conduit means between said pump means and said outertub for permitting generally free flow of liquid from said outer tubtoward said external drain as during said extraction operation and forpreventing flow of liquid into said outer tub from said conduit means.

3. In an apparatus for performing a washing operation and a liquidextraction operation as defined in claim 2 wherein said check valvemeans is disposed in said conduit means at the outlet of said outer tuband is responsive to movement of residual liquid in said conduit meanstoward said outer tub for operating to a closed condition to preventflow of said residual liquid from said conduit means into said outertub.

4. In an apparatus for performing a washing operation and a liquidextraction operation as defined in claim 2 wherein said check valvemeans defines a vertically oriented passageway nd wherein said checkvalve means includes a buoyant valve member responsive to reverse flowof liquid in said conduit means for operating to a closed condition toprevent flow of liquid into said outer tub from said conduit means.

5. In an apparatus for performing a washing operation and a liquidextraction operation as defined in claim 2 wherein said check valvemeans is operable for effecting a low pressure seal upon the cessationof pumping to prevent backflow of liquid into said outer tub from saidconduit means and further operable for effecting a high pressure seal toprevent backflow of liquid into said outer tub from said conduit meansduring said washing operation.

6. In an apparatus for performing a washing operation and a liquidextraction operation, the combination comprising: means for effectingsaid washing and liquid extraction operations including an outer tub forcontaining washing liquid and having a drain outlet in a lower portionthereof, a perforate inner tub for containing articles to be washed insaid liquid, and agitation means within said inner tub; means includinga reversible motor operable in a first direction for operating saidagitation means during said washing operation and operable in a seconddirection for rotating said inner tub during said extraction operation;conduit means effectively connecting said drain outlet to an externaldrain standpipe having an inlet located approximately the height of anupper portion of said outer tub;

bidirectional pump means associated with said conduit means and drivenby said reversible motor for effecting a pressure head in the directionof said outer tub with said motor operating in said first direction asduring said washing operation and for effecting flow of washing liquidfrom said outer tub toward said external drain when said motor isoperated in said second direction as during said extraction operation;and selfactuating one-way check valve means in said conduit meansadjacent said outlet and operable for permitting generally free flow ofliquid from said outer tub toward said external drain standpipe asduring said extraction operation and for preventing used washing liquidremaining in said conduit means from flowing into said outer tub aftertermination of said extraction operation.

7. In an apparatus for performing a washing operation and a liquidextraction operation as defined in claim 6 wherein said check valvemeans is responsive to backflow of liquid in said conduit means upontermination of said extraction operation for effecting a sealedcondition to prevent residual liquid in said conduit means from flowinginto said outer tub.

8. In an apparatus for performing a washing operation and a liquidextraction operation as defined in claim 6 wherein said check valvemeans is responsive to the relatively low urging force of liquid tendingto backflow ll'l he direction toward said outer tub for effecting asealed condition to prevent backflow into said outer tub upontermination of said extraction operation and wherein said check valvemeans is further responsive to the relatively higher urging force ofpressure in said conduit with said motor operating in said firstdirection for maintaining said seal to prevent flow of liquid into saidouter tub during said washing operation.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patan:No.3,691,797 7 Datmi September 19, 1972 Inventor(s) Thomas R. Smith It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Abstract, line 8 "tube" should be tub Col. 1, line 42 After "machine"insert liquid Col. 1, line 44 Delete "operable in" Col. 1, line 65"actuable" should be actuatable Col. 2, line 43 "actuable" should beactuatable Col. 2, lines 66 Delete "thru inclusive shown" & 67

C01. 3, lines 10 Delete "The main drive pulley 40 is drivingly & ll 99with the main drive pulley 40."

Col. 3, line 14 "show" should be shown Col. 3, line 49 Delete "the"(first occurrence) and insertfrom Col. 3, line 59 After "of" insert theCol. 4, line 39 After "holes 67," insert to Col. 7, line 10 "nd" shouldbe and Signed and sealed this 6th day of March 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM PO-IOSO (10*69) USCOMM-DC 60376-P69 11 us. GOVERNMENTPRINTING OFFICE 190 0-- 368-134

1. In an apparatus for performing a washing operation and a liquidextraction operation, the combination comprising: means for effectingsaid washing and liquid extraction operations including an outer tub forcontaining washing liquid and having a drain outlet in a lower portionthereof, a perforate inner tub for containing articles to be washed insaid liquid, and agitation means within said inner tub; means includinga motor for operating said agitation means during said washing operationand for rotating said inner tub during said extraction operation;conduit means effectively connecting said drain outlet to an externaldrain; pump means associated with said conduit means and driven by saidmotor for effecting flow of washing liquid from said outer tub towardsaid external drain when said motor is operated as during saidextraction operation; and one-way check valve means in said conduitmeans and operable for permitting generally free flow of liquid fromsaid outer tub toward said external drain as during said extractionoperation and responsive to residual liquid in said conduit means forpreventing backflow of said residual liquid into said outer tub.
 2. Inan apparatus for performing a washing operation and a liquid extractionoperation, the combination comprising: means for effecting said washingand liquid extraction operations including an outer tub for containingwashing liquid and having a drain outlet in a lower portion thereof, aperforate inner tub for containing articles to be washed in said liquid,and agitation means within said inner tub; means including a reversiblemotor operable in a first direction for operating said agitation meansduring said washing operation and operable in a second direction forrotating said inner tub during said extraction operation; conduit meanseffectively connecting said drain outleT to an external drain; pumpmeans associated with said conduit means and driven by said reversiblemotor for effecting a pressure head in the direction of said outer tubwith said motor operating in said first direction as during said washingoperation and for effecting a pressure head in the direction of saidexternal drain when said motor is operated in said second direction asduring said extraction operation; and one-way check valve means in saidconduit means between said pump means and said outer tub for permittinggenerally free flow of liquid from said outer tub toward said externaldrain as during said extraction operation and for preventing flow ofliquid into said outer tub from said conduit means.
 3. In an apparatusfor performing a washing operation and a liquid extraction operation asdefined in claim 2 wherein said check valve means is disposed in saidconduit means at the outlet of said outer tub and is responsive tomovement of residual liquid in said conduit means toward said outer tubfor operating to a closed condition to prevent flow of said residualliquid from said conduit means into said outer tub.
 4. In an apparatusfor performing a washing operation and a liquid extraction operation asdefined in claim 2 wherein said check valve means defines a verticallyoriented passageway nd wherein said check valve means includes a buoyantvalve member responsive to reverse flow of liquid in said conduit meansfor operating to a closed condition to prevent flow of liquid into saidouter tub from said conduit means.
 5. In an apparatus for performing awashing operation and a liquid extraction operation as defined in claim2 wherein said check valve means is operable for effecting a lowpressure seal upon the cessation of pumping to prevent backflow ofliquid into said outer tub from said conduit means and further operablefor effecting a high pressure seal to prevent backflow of liquid intosaid outer tub from said conduit means during said washing operation. 6.In an apparatus for performing a washing operation and a liquidextraction operation, the combination comprising: means for effectingsaid washing and liquid extraction operations including an outer tub forcontaining washing liquid and having a drain outlet in a lower portionthereof, a perforate inner tub for containing articles to be washed insaid liquid, and agitation means within said inner tub; means includinga reversible motor operable in a first direction for operating saidagitation means during said washing operation and operable in a seconddirection for rotating said inner tub during said extraction operation;conduit means effectively connecting said drain outlet to an externaldrain standpipe having an inlet located approximately the height of anupper portion of said outer tub; bidirectional pump means associatedwith said conduit means and driven by said reversible motor foreffecting a pressure head in the direction of said outer tub with saidmotor operating in said first direction as during said washing operationand for effecting flow of washing liquid from said outer tub toward saidexternal drain when said motor is operated in said second direction asduring said extraction operation; and self-actuating one-way check valvemeans in said conduit means adjacent said outlet and operable forpermitting generally free flow of liquid from said outer tub toward saidexternal drain standpipe as during said extraction operation and forpreventing used washing liquid remaining in said conduit means fromflowing into said outer tub after termination of said extractionoperation.
 7. In an apparatus for performing a washing operation and aliquid extraction operation as defined in claim 6 wherein said checkvalve means is responsive to backflow of liquid in said conduit meansupon termination of said extraction operation for effecting a sealedcondition to prevent residual liquid in said conduit means from flowinginto said outer tub.
 8. In an apparatus for performing a washingoperAtion and a liquid extraction operation as defined in claim 6wherein said check valve means is responsive to the relatively lowurging force of liquid tending to backflow in the direction toward saidouter tub for effecting a sealed condition to prevent backflow into saidouter tub upon termination of said extraction operation and wherein saidcheck valve means is further responsive to the relatively higher urgingforce of pressure in said conduit with said motor operating in saidfirst direction for maintaining said seal to prevent flow of liquid intosaid outer tub during said washing operation.